Means for minimizing inductive interference.



C. F. SCOTT.

MEANS FOR MINIMIZING INDUCTIVE INTERFERENCE.

APPLICATION FILED JAN-2,1915.

1,196,301. Patented Aug. 29, 1916.

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CHARLES E. SCOTT, OF NEW HAVEN, CONNECTICUT, ASSIGNOR TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

MEANS FOR MINIMIZING INDUCTIVE INTERFERENCE.

Specification of Letters Patent.

Patented Aug. 29, 1916.

Application filed January 2, 1915. Serial No. 171.

17 b all whom it may concern:

Be it known that I CHARLES F. SCOTT, a citizen of the United States, and a resident of New Haven, in the county of New Haven and State of Connecticut, have invented a new and useful Improvement in Means for Minimizing Inductive Interference, of which the following is a specification.

My invention relates to means whereby electric current flow may be substantially confined to certain conducting paths in preference to other paths which may be of lower impedance, and which may be electrically connected in parallel relationship therewith.

As explained in my application, Serial No. 170, filed concurrently herewith, and assigned to the lVestinghouse Electric and Manufacturing Company, it is desirable to maintain substantially the return flow of trolley currents of a railway system to the track rails in preference to ground or earth return with which the track rails may be in contact. By thus confining the return [low of trolley currents to the track, inductive disturbances which arise from the currents flowing in the railway system and which may be imposed upon an intelligence-transmission circuit disposed in proximity thereto, may be greatly minimized. Another advantage accruing from the above-mentioned arrangement is the substantial elimination of electrolytic corrosion of water mains, gas mains, etc., which might be occasioned by flow through the ground, of electric currents originating in electrical railway systems. To this end, I propose that series transformers be inserted, at spaced intervals, in a railway system, the primary windings of the transformers being connected across insulating joints and in series circuit relationship with the trolley conductor, and the secondary windings, preferably having the same number of turns as the aforementioned primary windings, being connected, at corresponding points, in the rail conductor and across insulating joints that divide the rail conductor into a series of track sections insulated from one another. By this means, the trolley currents and the rail currents may be maintained equal because of the relationship existing between the ampere turns of the primary windings and of the secondary windings of transformers, By reason of these insulating joints being inserted in the trolley conductor, as above mentioned, certain disadvantages arise, such as the necessity of using a non-contiguous trolley conductor with which the moving contact members of the railway vehicles must engage and the necessity of intermittently short circuiting the primary windings of the series transformers when such moving contact members momentarily bridge these insulating oints, etc.

By means of the present invention, I eliminate the insulating joints in the trolley conductor and effectively utilize series transformers which inductively link the trolley and rail conductors to maintain the return flow of the trolley currents substantially in the rail conductor.

Other features of novelty and advantages of my invention will be pointed out with particularity in the appended claims and will be set forth in the following description and in the accompanying drawing to which reference may now be had.

Figure 1 is a diagrammatic representation of a railway system, comprising a trolley conductor and a track, which is provided with an embodiment of my invention, and Fig. 2 is a. diagrammatic view of a modification of the. system shown in Fig. 1.

In Fig. 1, an electric railway system, which comprises a trolley conductor 1 and a track 2, is supplied with alternating current from any suitable source as, for instance, a single-phase alternator 3. The trolley conductor 1 comprises relatively low impedance conducting sections 1, preferably made of copper, and relatively high-impedance conducting sections a which may be made of bronze or iron and which are alternately spaced with the sections 1. The track 2 is shown as composed of two rails 5 which are electrically connected in parallel relationship by means of' conducting bonds 6 inserted adjacent to insulating joints 7 that are disposed at spaced intervals in each rail 5. The high-impedance sections 4.- of the trolley conductor 1 are shunted by primary windings 8 of series transformers 9, the secondary windings 10 of which are connected, as shown, to the track and across the insulating joints 7. An intelligencetransmission conductor 11 which, in this instance, is shown as a telegraph conductor, is disposed in proximity to the railway system and subjected to the inductive dis turbances arising from the currents flowing in the railway system.

When a moving vehicle receives power from the trolley conductor 1, the return flow of the trolley currents is confined to the track 2 because of the relationship existing between the ampere turns of the primary windings and the secondary windings of the transformers 9. By thus inductively inter-linking the trolley conductor 1 and the track 2, electromotive forces are impressed at intervals up on the track 2 by the secondary windings 10 of the transformers 9. Tn this manner, the substantially high impedance of the track is overcome, permitting the trolley currents to flow therethrough in preference to a ground or earth return.

In commercial installations, it may be desirable to spac the transformers 9 at intervals of one mile, and, in this instance, the

high-impedance conducting sections 4 of the trolley conductor 1 may be from 500 to 1000 feet in length. While the trolley conductor sections 4 may have substantially high impedances, they will be so made as to supply the necessary currents to moving vehicles that are in contact with these sections without undue heat losses being developed therein. Copper conductors, which comprise a large portion of the trolley conductor 1, are utilized as feeders 12 and are connected in parallel with the high impedance trolley conductor sections 4 to carry the main portion of the trolley currents through the primary windings 8 of the transformers 9. It will be understood that the high-impedance conducting sections 4 are so disposed as to be engaged by the moving contact members or current-collecting devices upon the vehicles. Adjustable taps 13 and 14 are shown on the transformer winding 8 and 10, respectively, in order to regulate the amount of current flowing through the track and the earth and to compensate for the unequal spacing of the telegraph conductor 11 with respect to the railway system. The advantage arising from the foregoing arrangement of the trolley circuit 1 is chiefly dependent upon the elimination of all insulating joints in the trolley conductor.

In Fig. 2, the track is shown divided into alternately short and long sections 15 and 16, respectively. The short sections 15 are disposed at points in thetrack 2 which correspond to the disposition of the high-impedance conducting sections 4 in the trolley conductor 1. As above explained, the primary windings 8 of the series transformer 9 are connected in parallel relationship with the high-empedance trolley conductor sections 4. The secondary windings 10 are c0nnected in parallel with the short rail sections 15 and in series relationship in the track 2. The transformer 9 is preferably constructed as shown in Fig. 2 in order that the coils constituting the secondary winding 10 may embrace independent magnetic circuits such as are provided by the different legs of the core member. In view of this construction, the short-circuiting of one of the coils will not effect the electromotive force impressed by the other coil. Conductors 17, connected to the terminals of the secondary windings 10, constitute feeders which are connected, in turn, to the conducting bonds 6 inserted on each side of the insulating joints 7 1nasmuch as the impedance of the short track sections 15 may be so low as to shunt away from the secondary windings 10 undue amounts of current, or, inasmuch as these short track sections may act as short circuited paths for the secondary windings 10, the insulating joints 7 are inserted and bridged by impedance devices or choke coils 18. By spacing the choke coils 18 a sufficient distance from each other, as shown in Fig. 2, passing trains will not short circuit both of the coils 18 at the same time. The electromotive forces impressed upon the secondary windings 10 by the primary windings 8 will be divided between the two impedance coils 18 connected in series so as not to stress unduly the insulating joints 7.

In the system shown in Fig. 2 the return flow of the trolley currents is confined to the long track sections 16 and the alternately disposed short track sections 15 which are shunted by the low-resistance feeders 17. As a result, the magnetizing disturbances arising from the current flow over the trolley conductor 1 will be substantially neutralized by the equal and opposite magnetizing disturbances arising from the current flow over the track circuit 2.

While I have shown and described the track circuit as comprising two rails 5 which are connected in parallel relationship, it will be understood that one rail may be used as a return conductor for the trolley currents. Moreover, it is obvious that the transformers 9 may be utilized to confine the return flow of trolley currents to return feeders other than the track 2, and, in this manner, keep the trolley currents out of the track instead of compelling them to flow through the track.

While 1 have shown and described several embodiments of my invention, it will be apparent that many modifications may be made without departing from the spirit and scope of the appended claims.

"Whenever throughout the specification and claims the term impedance is employed, it is intended to mean resistance, if the conditions are such as to render the introduction of impedance in the circuit undesirable, and they should be read accordingly.

I claim as my invention:

1. A railway system comprising a source ofv current supply, a trolley conductor comprising a plurality of conducting sections, alternate sections of. which are of relatively high impedance, a track, and means connected across said high-impedance sections of the trolley conductor to inductively link the trolley conductor and the track.

2. A railway system comprising a source of current supply, a trolley conductor connected thereto and constituting conducting sections of alternately high and low impedance, a track, and means connected across said high-impedance trolley conductor sections to impress electromotive forces at intervals on the track.

3. A railway system comprising a source of current supply, a trolley conductor connected thereto and containing conducting sections of relatively high and low impedance, said sections being alternately spaced, a track in contact with the earth, and inductive means connected across said highimpedance trolley conductor sections to confine current fiow to the track in preference to the earth.

4. A system of distribution comprising a source of current supply, a conductor con nected thereto and constituting conducting sections of alternately high and low impedance, a second conductor, and means connected in shunt to the high-impedance conducting sections of the first named conductor to compensate for the impedance of the second named conductor.

5. A system of distribution comprising a source of current sup-ply, a conductor connected thereto and comprising conducting sections of alternately high and low impedance, a second conductor comprising a plurality of spaced conducting sections, and transformers serving to interlink inductively the said conductors, the primary windings of the transformers being connected in shunt to the high-impedance conducting sections of said first conductor, and the secondary windings being connected to adjacent spaced conducting sections of said second conductor.

6. A system of distribution comprising a source of current supply, a conductor connected thereto and comprising conducting sections of alternately high and low impedance, a second conductor, insulating joints interposed at intervals therein, and spaced transformers inductively interlinking the said conductors, the primary windings of the transformers being connected in shunt to the high-impedance conducting sections of said first conductor, and the secondary windings being connected across the insulating joints of the said second conductor.

7. A railway system comprising a source of current supply, a trolley conductor connected thereto and comprising conducting sections of alternately high and low impedance, a track provided with spaced insulating: joints, and transformers serving to link. inductively the trolley and track conductors, the. primary windings of the transformers being connected. in shunt to the high-impedance conducting trolley conductor sections, and the secondary windings being connected to the track and across the insulating joints disposed therein.

8. A railway system comprising a source of current supply, a trolley conductor, a track comprising a plurality of rail sections insulated from one another, transformers for inductively interlinking the trolley conductor and the track, primary windings of the transformers being inserted in series relationship with the trolley conductor, and the secondary windings being connected to track sections adjacent to intermediate track sections, and impedance coils electrically connecting said intermediate track sections to said track sections electrically connected to the secondary windings.

9. A railway system comprising a source of current supply, a trolley conductor connected thereto, a track comprising a plurality of long and short rail sections alternately spaced and insulated from one another, transformers inductively interlinking the track and the trolley conductor, primary windings of the transformers being connected at intervals in series circuit with the trolley conductor, and secondary windings being connected to adjacent long rail sections, and impedance devices electrically connecting the short rail sections to the said long rail sections.

10. A railway system comprising a source of current supply, a trolley conductor connected thereto and comprising conducting sections of alternately high and low impedance, a track comprising a plurality of alternately long and short rail sections insulated from one another, transformers inductively interlinking the track and the trolley conductor, primary windings of the transformers being connected in shunt to said high-impedance conducting sections of the trolley conductor, and secondary windings being connected to adjacent long rail sections, and impedance devices electrically connecting the short rail sections to the long rail sections.

11. A system of distribution comprising a source of current supply, a conductor comprising conducting sections of alternately high and low impedance, a second conductor comprising a plurality of conducting sections insulated from one another, spaced transformers serving to inductively interlink the said conductors, the primary windings of the transformers being connected in shunt to the high-impedance sections of said first conductor, and secondary windings being so connected to sections of said second conductor as to provide intermediate secsubscribed my name this 28rd day of Dec. tions thereof, and impedance devices'elec- 1914.

trically connecting said intermediate sections of the second conductor to the sections CHARLES SCOTT 5 thereof which are connected to said secondi/Vitnesses:

ary windings. B. B. HINEs, In testimony whereof, I have hereunto M. O. MERZ.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. C. 

